Freestanding Block Copolymer Membranes with Tunable Pore Sizes Promoted by Subnanometer Nanowires

Abstract Block copolymers (BCPs) have enduring appeal for its intriguing assembly behaviors. Nevertheless, the unsatisfactory mechanical properties of BCPs make it a problem to fabricate freestanding membranes and hindered practical applications. Herein, a freestanding membrane with tunable pore size is prepared simply by co‐assembly of BCPs and subnanometer nanowires (SNWs), combining the abundant function of BCPs and prominent mechanical properties of SNWs. Benefited from synergy of the components and the hierarchical structure, the tensile strength of composite membrane is promoted by two orders of magnitude compared to that of BCPs. With the columnar pores aligning vertically to surfaces and the pore size regulated by processing conditions, the membranes exhibit precise size‐selected effect in ultrafiltration of Au nanoparticles (Au NPs) and can distinct NPs with diameter difference as tiny as 5 nm, demonstrating the promising prospect in separation technology and even widespread fields.